String trimmers long have been used to cut vegetation, particularly in areas inaccessible by a lawn mower or other cutting device. Typically, a string trimmer utilizes one or more flexible flails, such as a string fabricated of a plastic polymer, which is retained within a head assembly. In most string trimmers, the head assembly includes a spool for storing a large quantity of flail (string) therein together with a feeding mechanism for feeding the flail into a cutting path. These feeding mechanisms may be of the bump-feed type, the inertial-feed type, or a type that utilizes an actuator that is operable to feed string when a button or lever is pushed.
Prior to the advent of feeding mechanisms, string trimmers utilized a fixed length of string, which was replaced manually once wear had occurred beyond a certain point. Because of the need to replace the flail frequently, it initially was believed that feeding mechanisms would provide a better alternative to the user, who thereby would not be faced with the inconvenience of manually replacing the string at frequent intervals. However, the stored string tends to tangle and become fouled, and in certain circumstances can become welded to itself, thereby preventing proper operation of the feeding mechanism. In addition, reloading the spool with a supply of fresh string can be a complicated process, not easily undertaken by the typical consumer. Furthermore, the single most common reason for return of string trimmers is tangled flails in the bump head.
Patents disclosing string trimmers that utilize one or more replaceable flails include Doolittle et al. U.S. Pat. No. 4,089,114, Jacyno et al. U.S. Pat. No. 4,118,865, Rouse U.S. Pat. No. 4,756,146 and Tuggle U.S. Pat. No. 5,303,476. The above-identified Doolittle et al. '114 patent further discloses the use of a disposable tip member, which snap-fits into a rotatable truncated cone member and a strand is secured within the disposable tip member.